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Myth: only the mother's side matters | CION Cancer Clinics
An inherited cancer gene fault can come from your father just as easily as from your mother. Most of these genes sit on chromosomes both parents pass on equally, to sons and daughters alike. The father's side is missed so often because men who carry breast and ovarian cancer faults rarely become ill themselves. This page explains how that happens and what to ask about both sides. At CION Cancer Clinics, our team helps carriers and their families plan checks, next steps and support after a genetic result.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Does inherited cancer risk only come from the mother's side?
- How does a fault travel down the father's side?
- How can you gather your father's side of the family history?
- The inheritance terms, in plain language
- What families assume about the father's side, and what is true
- What this page cannot tell you
- Four things families say about the father's side
- Common questions about the father's side of the family
The short answer
Does inherited cancer risk only come from the mother's side?
No. A fault linked to cancer can pass from either parent, and each child of a carrier parent, son or daughter, has a one in two chance of inheriting it. Your father's sisters, his mother and his cousins matter just as much as your mother's.
Why families look only at the mother
Breast and ovarian cancer are the cancers most families connect with inheritance, and they happen to women. When a mother, her sister and her mother have all had breast cancer, the pattern is plain to see. When the same fault sits on the father's side, it may pass through a healthy father and his healthy brothers, and nobody sees a pattern at all.
What it costs to ignore the father's side
Daughters whose risk comes through their father may never be offered screening. Sons are rarely told they could carry and pass on a fault, or that some faults raise their own risk of prostate, pancreatic or breast cancer. A family tree has to include both sides to be of any use.
When a counsellor asks about your father's family, it is not a formality.The father's side
How does a fault travel down the father's side?
The route is the same as on the mother's side. What changes is how visible it is.
Through a healthy father
He carries the fault in every cell, including his sperm. He may never become ill, especially if the fault mainly causes breast or ovarian cancer. Each of his children has an even chance of inheriting it.
Through his female relatives
The clues on the father's side are usually the women. An aunt with ovarian cancer, or a grandmother with breast cancer at a young age, counts exactly as much as the same diagnosis on your mother's side.
Relatives to ask about
- Your father's sisters
- His mother and her sisters
- His female cousins
Through the men themselves
Some faults raise men's own risk. Men who carry certain breast cancer faults can develop prostate, pancreatic or breast cancer, so their diagnoses belong on the tree too.
The rare exceptions
For a few rare genes, which parent passed the fault changes the risk. In one known example, linked to rare tumours of the head and neck, the fault mainly causes illness when it comes from the father. Your counsellor will say if your family's gene is one of these.
Not sure whether this applies to you?
Ask an oncologistBefore the appointment
How can you gather your father's side of the family history?
Start with your father, if you can
Ask about his parents, brothers, sisters and cousins. Who had cancer, what kind, and at roughly what age.
Ask his sisters directly
Women on the father's side often know more about women's illnesses than the men do. Some diagnoses were never shared with him.
Include the men's diagnoses
Prostate, pancreatic and male breast cancer on the father's side are all worth writing down, with ages where known.
Note what nobody knows
Relatives who died young, or of an illness nobody named, are gaps. Writing them down helps the counsellor judge how much the tree can show.
Bring both sides together
Put your mother's family and your father's family side by side on one sheet. The counsellor will draw them into a single tree.
Words you will hear
The inheritance terms, in plain language
- Autosomal
- Carried on one of the chromosomes both parents pass on equally. Most inherited cancer genes are autosomal.
- Dominant
- One faulty copy is enough to raise risk. Each child of a carrier has a one in two chance of inheriting it.
- Paternal and maternal
- Paternal means from the father's side of the family. Maternal means from the mother's side.
- Obligate carrier
- A relative who must carry the fault because it passed through them, such as a healthy father whose daughter and sister both carry it.
- Penetrance
- How often a fault leads to cancer across everyone who carries it. It is never all of them, and it can differ between men and women.
- Pedigree
- The family tree a counsellor draws, covering both sides and several generations.
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Side by side
What families assume about the father's side, and what is true
What families assume
What is actually true
Daughters inherit only from their mother
Sons and daughters inherit from either parent equally
A healthy father cannot pass anything on
A healthy father can carry and pass on a fault
The father's sisters are another family's concern
His sisters are your close relatives for risk
Men do not need testing
Men can be tested, and some need screening
Being straight with you
What this page cannot tell you
It cannot tell you which side of your family a fault came from, or whether there is one at all. Only a family tree covering both sides, and sometimes a test on a relative who had cancer, can answer that.
It cannot interpret a relative's result
If an aunt on your father's side has a report, what her specific variant means for you is a question for the counsellor who ordered the test. Bring a copy, with her permission, to your own appointment. The exact wording on the report matters.
Who this does not apply to
Most people have some cancer on each side of the family, and most of it is not inherited. If your father's side has one relative diagnosed at an older age, with no young diagnoses or rare cancers, it probably changes nothing for you. The point is to count both sides equally. It is not a reason to worry about both.
Studies of how often the father's side is missed are still small, and mostly from outside India.Commonly believed
Four things families say about the father's side
"My father's family is healthy, so the risk is only from my mother."
A father can carry a fault without being ill, and so can his brothers. Look at his sisters, his mother and his aunts before deciding that side is clear.
"Breast cancer genes pass only from mother to daughter."
A father passes them to his daughters just as often as a mother does. He can also pass them to his sons, who can pass them on in turn.
"Men do not need to know about breast cancer genes."
Men who carry some of these faults have a raised risk of prostate, pancreatic and breast cancer themselves. Their children may also need testing.
"My mother tested negative, so our family is clear."
Her result covers her side, for the fault that was looked for. Your father's side has not been tested at all, and may still need attention.
Questions we are asked
Common questions about the father's side of the family
Can I inherit a breast cancer gene from my father?
Yes. A father who carries a breast and ovarian cancer fault can pass it to any of his children, with a one in two chance for each. He may never have had cancer himself, which is why his side is so often overlooked.
Am I more likely to inherit my father's fault than my brother is?
No. Sons and daughters have exactly the same chance of inheriting it. What differs is what the fault means for each of them, since some faults mostly raise the risk of cancers in women.
My father's sister had ovarian cancer. Does that affect me?
It may. Ovarian cancer on either side is one of the stronger reasons to consider testing. The best first step is testing your aunt, if she is willing, since her result tells the family whether there is a fault to look for.
Should my father be tested even though he is healthy?
Sometimes. If a fault is already known in his family, testing him shows whether it came down your branch. If he tests negative for that fault, his children usually need no test for it.
Is there a cancer gene that passes only through mothers?
For inherited cancer risk, essentially no. Almost all the genes involved sit on chromosomes both parents pass on. A few rare genes behave differently depending on the parent, and your counsellor will tell you if yours is one.
My father died before I could ask about his family. What now?
Ask his brothers, sisters or cousins, and anyone who knew his parents. Old hospital papers can help. Tell the counsellor what is unknown, since gaps are common and they plan around them.
Are men screened if they carry a fault?
Depending on the gene, men may be offered prostate checks, breast checks or other screening. The plan depends on the exact fault and the family history, and it is agreed with a specialist.
Who should I talk to about both sides of my family?
A genetic counsellor or your oncologist. Bring a list of relatives with cancer on both sides, with rough ages. If you are unsure who to approach, call the CION helpline and someone will point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
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Sources
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
- National Cancer Institute — BRCA Gene Changes: Cancer Risk and Genetic Testing
- Cancer Research UK — Inherited cancer genes and increased cancer risk
- NHS — Predictive genetic tests for cancer risk genes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Cancer risk from the father's sideThe father's line, explained in fullDoes it matter which parent it came from?The rare genes where the parent changes the riskMyth: only women carry breast cancer genesWhat a breast cancer fault means for menBuilding your family treeHow to record both sides before an appointment
Talk to us
Not sure what your father's side means for you?
Tell us who was diagnosed on each side of your family, and at what age. We will tell you honestly whether a genetic referral is worth making. One helpline serves every CION centre.